1. Field of the Invention
The present invention relates to an overlapped-transfer preventing paper supply device for use in an image forming apparatus such as an electrophotographic copying machine and a printer.
2. Prior Art
For example, an electrophotographic copying machine includes a device for supplying a transfer portion with a non-copied sheets one-by-one each time a paper supply signal is generated, an intermediate paper supply device for enabling copying on both sides of a sheet for supplying a transfer portion with a sheet one side of which has been copied each time a paper resupply signal is generated, or a paper supply device for supplying an appointed position of a manuscript-table with a manuscript sheet each time a paper supply signal is generated.
Such paper supply devices include an overlapped-transfer preventing arrangement wherein an overlapped-transfer preventing member, such as a friction pad or a pad roller, is arranged so as to be engaged with a rotary paper supply member to prevent the double transfer of sheets by so-called frictional separation, or an overlapped-transfer preventing arrangement wherein a pad roller and rotary paper supply member are arranged so as to be partially overlapped such that a sheet passing between such members is caused to have a zigzag shape, thereby preventing double transfer of sheets by the firmness of the sheets.
However, in the above described overlapped-transfer preventing arrangement or devices, a sheet which has been subjected to an overlapped-transfer preventing operation moved is away from a sheet source or supply, such as a paper supply cassette or a paper supply deck. Thus, the leading end of such sheet is positioned in the vicinity of an overlapped-transfer preventing portion of a sheet transfer path that includes the overlapped-transfer preventing member and the rotary paper supply member that sometimes is positioned into the overlapped-transfer preventing portion.
Under such the condition, if the paper supply cassette then is removed or if a paper-placing plate of the paper supply deck is lowered, to enable the paper supply cassette, the paper supply deck, or the like to be provided with sheets, such sheet which has been subjected to the overlapped-transfer preventing operation remains in the paper supply portion. When subsequently the paper supply cassette, the paper supply deck or the like are replaced or set for further operation, not only will the sheet left in the paper supply portion be smashed to an extent to be useless but also jamming of following sheets will occur due to such damaged or smashed sheet.